North West Bay

North West Bay is a relatively sheltered open estuary up to about 35 metres deep. The wide entrance, which opens at the northern end of the D’Entrecasteaux Channel, is sheltered from the open ocean by Bruny Island (Temby & Crawford, 2008).

Intertidal saltmarsh and mudflats are extensive in the northern part of the Bay and seagrass beds occur in shallow water along the western shoreline, the most common species being Tasman grasswrack (Heterozostera tasmanica) (Temby & Crawford, 2008).

North West Bay Succulent saltmarsh

Succulent saltmarsh

A recent study (Mount & Otera, 2011) has shown that the extent of seagrass habitat in North West Bay has been in long term decline over the past 60 years. In particular, large changes were evident in the mid-1980s at Barretta and Clarkes Beach, Coningham. However, since 2008, the seagrass beds have been recolonising areas previously occupied and increasing in density. 

The Bay is habitat for many fish and macroinvertebrate species. 54 macroinvertebrate species are known to occur including worms, sea snail, shrimp, sandhopper, crab and sea urchin (Temby & Crawford, 2008). The endangered Spotted handfish is also known to occur here.

The area is highly valued by the community as a place to live and play with numerous beaches (Snug Beach, Peggys Beach, Coningham Beach), parks (Dru Point Reserve, Snug, Inverawe Native Garden), boat ramps and jetties (Dru Point Boat Ramp and Margate Jetty).

Industrially, North WestBay is used for boat construction, and marine farming, as well as acting as a source to assimilate sewage, processing waste and various forms of catchment and stormwater runoff (Jordan et al.2002).

The State of the D’Entrecasteaux Channel and the lower Huon Estuary report (Parsons, 2012) states the following about North WestBay:

  • At risk from nutrient loading due to high terrestrial inputs of nutrients and reduced flushing times
  • Experiences turbidity values far in excess of the upper national guideline value during high flows of the North WestBayRiver
  • Dissolved oxygen (DO) levels in North WestBay are variable and have dipped as low as 58% saturation in bottom waters during summer, reflecting poor environmental health
  • Occasional elevated values of contamination highlight the vulnerability of some beaches and other recreational sites to short‐term spikes in bacterial loads. Primary areas of concern in recent years include Margate and Snug
  • Evidence of environmental legacy issues at the former heavy industrial site at Electrona, although measures have been implemented to mitigate impacts on the Channel
  • Heavy metals are also elevated in sediments in deep, silty areas of North WestBay

Continued use of North West Bay by the community and commercial users is dependent on its long-term ecological health and productivity. The D’Entrecasteaux Channel Project aims to assist in this process 

Sources:

Jordan, A., Doole, J., Archer, L., Lawler, M., Halley, V., and Sanderson, C., 2002, Assessment and monitoring of nutrients and habitats in North West Bay: Supporting Sustainable Management. Kingborough Council Natural Resource Management Strategy, Hobart.

Mount R. E. and K. Otera, 2011, The status of seagrass extent in North West Bay. A technical report for the Kingborough Council by the Blue Wren Group, School of Geography and Environmental Studies, University of Tasmania, Hobart, Tasmania.

Parsons, K. E. (2012). State of the D’Entrecasteaux Channel and the lower Huon Estuary 2012. Report for the D’Entrecasteaux Channel Project, Ecomarine Consulting, Tasmania.

Temby, N and Crawford, C. 2008, Coastal and Estuarine Resource Condition Assessment: A baseline survey in the Southern NRM Region, Tasmania, Tasmanian Aquaculture and Fisheries Institute, University of Tasmania, SandyBay.

 

 

© 2011 Kingborough Council
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